1. Field of the Invention
The present invention relates to an improved process for simultaneously upgrading tar sand bitumen (organic liquid material) and liquifying solid coal. More particularly, the invention relates to a process wherein bitumen from bitumen-containing tar sands, with or without at least partial separation from the sand, is mixed with a high percentage of solid, comminuted coal particles to form a liquified mixture which is then coreacted only with hydrogen at elevated temperature and pressure. Desirably, but not necessarily, the resultant liquid from such hydrogenated bitumen-coal mixture may be partially recycled as a solvent to remove bitumen from raw tar sands before the liquid bitumen is mixed with the coal.
2. Art of Interest
It is known in the art to produce coal oil by liquification of coal solids in a heavy solvent. It is also known to remove inorganic material from bitumen-containing tar sands using a solvent extraction process. The primary aim of each of these separate solvent liquification processes is to produce a heavy residuum material having distillable fractions without producing excess hydrocarbon gases or coke-like solid material.
In U.S. Pat. No. 4,330,390 to Rosenthal et al. (herein incorporated by reference), the patentees disclose simultaneous upgrading of coal and a heavy petroleum fraction. Finely divided coal is dissolved in a separate petroleum-derived "heavy" solvent such as hydrogenated polycyclic aromatic hydrocarbons as derived from asphaltic or naphthenic crudes in the presence of added hydrogen. The dissolved mixture is then subjected to hydrocracking conditions in the presence of a catalyst and a liquid coal oil effluent is withdrawn. While the process of Rosenthal et al. produces a liquid coal oil having a low specific gravity, low sulfur content, and low nitrogen content, a significant amount of solid residue remains in the product oil, without further refining, which renders the coal oil unsuitable for use as a transportation or heating fuel.
In U.S. Pat. No. 4,189,376 to Mitchell (herein incorporated by reference), bitumen is recovered from so-called tar sands in a vertically-extending solvent extraction zone, wherein a separate solvent for the bitumen (such as high aliphatics or aromatics or higher-boiling synthetic hydrocarbon fractions) is passed through the tar sands-containing extraction zone. A liquid, including the solvent and the extracted bitumen, are removed from the extraction zone. However, the solvent-extracted bitumen is relatively crude and requires significant upgrading in the presence of a catalyst to produce a useful range of hydrocarbon fractions.
U.S. Pat. No. 4,298,454 Aldridge et al. discloses a hydroconversion process for liquification of coal and a hydrocarbonaceous oil to produce liquid hydrocarbons with a minimum of gas production and coke formation. The disclosed hydroconverting process requires an added thermally decomposable metal compound as a catalyst to obtain the required conversion. In control examples where the decomposable metal catalyst was deleted, the hydroconversion of an admixture of tar sands bitumen and subdivided coal produced unacceptably high amounts of coke.
In U.S. Pat. No. 4,214,977, Ranganathan et al. disclose a process for the hydrocracking of a heavy hydrocarbon oil such as the bitumen oils removed from oil sands. The catalyst required for this hydrocracking is a subdivided coal and iron sulfate used in catalytic amounts up to 2 weight percent of the feedstock. In control experiments conducted in the absence of the catalyst, excess solids (coke) were produced and operability of the system was poor.
Canadian Pat. No. 1,160,586--S. E. Moschopedi, discloses a batch process in which a pulverized coal is slurryed in a separate solvent derived from an oil sand bitumen, a deasphalted bitumen, an oil fraction of bitumen, or a hydrotreated coker gas oil. The mixture is heated at 250.degree. to 500.degree. C. for a time long enough to liquify at least some of the coal. High pressure hydrogen is present, and optionally a hydrogenation catalyst. There is no suggestion that a high percentage of the feed is bitumen that is corefined with simultaneous liquification of the coal to form a single synthetic crude suitable as a refinery feed stock without further extensive treatment. The patentee discloses a batch liquification process for the conversion, and does not teach the use of the recovered liquids from the process as a suitable solvent for further liquification of coal.
Additional patents of general interest in the field include:
Johnson--U.S. Pat. No. 4,032,428 PA0 Rosenthal et al.--U.S. Pat. No. 4,330,393 PA0 Gatsis--U.S. Pat. No. 4,338,183 PA0 Rosenthal et al.--U.S. Pat. No. 4,350,582 PA0 Rosenthal et al.--U.S. Pat. No. 4,354,920 PA0 Dahlberg et al.--U.S. Pat. No. 4,376,037 PA0 Dahlberg et al.--U.S. Pat. No. 4,389,301 PA0 Ternan et al.--Canadian Pat. No. 1,073,389.
Bitumen may be separated from raw mined tar sands by a number of methods. These include, for example, direct coking of the tar sands, usually at operating temperatures of about 900.degree. F.; anhydrous solvent extraction, usually a light hydrocarbon with recovery of the solvent; cold water bitumen separation; hot water bitumen extraction; and the like. These processes are discussed in more detail in "The Tar Sands of Alberta, Canada" by F. W. Camp, 3rd ed., published by Cameron Engineers, Inc., 1315 S. Clarkson Street, Denver, Colo. 80210 in 1976, which is incorporated herein by reference.
The upgrading of the bitumen once separated usually has two objectives. The first objective is the conversion of froth (a product of some separation processes) to hydrocarbon bitumen. The second objective is the upgrading of the bitumen to a more saleable product generally described as a synthetic crude oil. These processes are described as refining of bitumen (conversion), visbreaking, hydrovisbreaking and refining. These methods are also described in more detail in "The Tar Sands of Alberta, Canada", noted above.
Additional background information and experimental data are also found in:
"Hydrocracking Athabasca Bitumen in the Presence of Coal, Part 1: A Preliminary Study of the Changes occurring in the Coal", by M. Ternan, B. N. Nandi and B. I. Parsons, Canadian Department of Energy Mines and Resources, Mines Branch, Fuels Research Centre, Ottawa, October 1974, Research Report No. R276.
"Hydrocracking of Athabasca Bitumen-Effect of Coal-Base Catalyst on Pilot Plant Operation" by C. P. Khulhe, B. B. Pruden and J. M. Denis, Energy, Mines and Resources, Canada, Canadian Centre for Mineral and Energy Technology, CANMET Report 77-35, January 1977.
"A Comparative Study of Fe Catalysts, ZnCl.sub.2 Catalysts and ZnCl.sub.2 -Promoted Fe Catalysts for Hydrocracking of Athabasca Bitumen" by W. A. O. Herrmann, L. P. Mysak and K. Belinko, Energy Mines and Resources Canada, CANMET Canadian Centre for Mineral and Energy Technology, CANMET Report 77-50, January 1977.
"The Chevron Co-Refining Process", by J. W. Rosenthal, et al., presented at the 49th Midyear Refining Meeting, Session on Heavy Oils Processing, Wednesday, May 16, 1984, New Orleans, La.
The patents and reports described hereinabove require an added catalyst in any subsequent upgrading (i.e., hydrocracking) step. These disclosures do not describe or suggest the present invention of continuously upgrading a combined feedstock of primary separated tar sands bitumen and subdivided coal by contact with hydrogen, but in the absence of added catalyst, preferably with recycling of the liquid product as a solvent for subsequent upgrading of bitumen extraction from the original tar sand or the instant coal-bitumen corefining process.